The effect of permethrin impregnated sisal curtains on vector density and malaria incidence: a pilot study

Impregnation of bednets and curtains with suitable pyrethroids may reduce entomological inoculation rates (EIR) and malaria incidence. We conducted a quasi-experimental pilot study over 3 months in Western Kenya on 20 houses with 54 children. Ten houses in the experimental site received sisal curtains treated with permethrin at either 0.5g/m2 or 0.1g/m2. Control houses had untreated curtains or none. Mosquito vector density (MVD), man biting rates (MBR), and residual insecticidal effects (RIE) of permethrin were determined every two weeks. MVD was reduced by 97.7% and 98.7% in houses from the 2 experimental groups with a 60% reduction with unimpregnated curtains. MBR varied from 6.4 (no curtains), 1.7 (unimpregnated), 0.7 (0.5g/m2 curtains) to 0.4 (1.0g/m2 curtains). RIE begun to decline after the fourth month. Malaria incidence remained similar at the two sites. We conclude that covering of eaves and windows with permethrin impregnated sisal curtains can reduce MVD and the number of mosquito bites to individuals sleeping in protected houses.